Questar

Welcome! This is designed as a short tutorial on using the Questar telescopes located at the Drew University observatory. It is important that you go through the steps from beginning to end as the instructions are sequential and you will miss valuable information by skipping around. Once you have been through the directions from start to finish you can skip from topic to topic to review if you wish. You may also find it helpful to print out the directions. The labeled diagram will be especially helpful to have on hand as you read the directions, and for when you arrive at the observatory to use the scope.

Thank you and here’s wishing you “good seeing”!

Parts

Questar Parts

The above picture shows all of the important parts of the Questar 3 1/2-inch telescope. Familiarize yourself with these parts. It may serve you well to print out the image and refer to it as you go through the rest of the directions. The controls with which you will need to become familiar are;

The eyepiece upper knurl (for initial eyepiece focusing)

The amplifying (Barlow) knob

The finder knob

The focus knob

The altitude (declination) knob

The azimuth (right ascension) knob

Normally you will not need to make adjustments to anything other than those knobs listed above. You will also need to know the location of the declination circle and the right ascension circle with its plastic index mark. You will need to know how to read these in order to point the telescope at any given set of celestial coordinates.

Initial Setup

When you arrive on the roof you will find that the Questar has already been set-up for you on wooden desk-like pedestals. All necessary alignment of the telescope has already been done and the telescope is now “Ready for viewing”. The above image shows the telescope with its lens cover removed and the correcting lens exposed. You should NEVER under any circumstances touch or attempt to clean the correcting lens (or any other lens in the Questar, including the eyepiece). The optics in the Questar are of very high quality and even the smallest scratch or smudge of oil can ruin your evening of star gazing and possibly permanently damage the telescope.

Right Ascension

To adjust the right ascension (R.A.) of the telescope, you use the knob located at the front of the base. This knob should turn smoothly and easily, providing a continuous motion of the scope about the R.A. axis. The Questar is built so that the motor drive can be left on and adjustments made by hand at the same time without causing damage to the drive. When you stop turning the knob, the motor will take over and continuously move the R.A. at the rate of the Earth’s rotation. To see the effect of the motor you can turn it off by using the line switch. The object in the scope’s field of view will soon drift out of view. Don’t forget to turn the motor back on again, and don’t leave it off too long.

Notice the numbered ring on the base. It is marked in both degrees and in hours of angle, hence the name “hour angle” (same as right ascension). This ring is free to turn and can be set to the known R.A. of a star on which the scope is set. If the motor is then left running for the rest of the night, you can locate any star in the sky if you know its R.A. (and its declination which will be discussed soon). The process of “setting” this ring is part the set-up procedure which is done for you (along with the earlier mentioned polar alignment). For this reason it is important that you not adjust the ring yourself unless instructed to do so.

Declination

We have covered how to adjust the right ascension axis already. The other axis which can be adjusted is the declination (dec.) axis. While the R.A. axis runs down through the center of the base and is aligned with the north celestial pole, the declination axis is perpendicular to this and runs straight across the barrel of the scope through the word “QUESTAR” in the above image. The dec. axis runs parallel to the equator. This orientation, along with the polar orientation of the R.A. axis, gives us the name of this type of mount – Polar Equatorial.

The adjustment knob for the dec. axis is pictured above. It is located on the right side of the scope, and like the R.A. knob, it should turn smoothly and easily providing a continuous motion. On the opposite side of the scope from this knob is located the declination scale and another similar knob. This knob locks the telescope into its current declination setting. It should be free and loose and turned all the way BACK to free the declination adjustment. Turn it fully FORWARD to lock the declination setting.

All of the knobs should move freely and smoothly. If they do not they are either locked in place or are binding and should be checked. Under no circumstance should you need to apply more than a minimal amount of force to these knobs. Forcing a knob which refuses to move could cause serious permanent damage to the precise and delicate works within the telescope.

Finder Mode

To begin viewing you will first need to find a star or other object. Unlike most telescopes the Questar has no finder scope. A finder scope is a smaller telescope which is mounted on the body of the main telescope. A finder scope is generally of low power and thus provides a large field of view making it easier to locate and center your target. Take a look at the telescope in the dome to see an example of a finder scope.

Although the Questar has no finder scope, it does have a functional equivalent to one. To use it you set the two knobs near the eyepiece to their outside positions as pictured in the left image above.

High Power Mode

Once you have found and centered an object, and adjusted the eyepiece, you are ready to move to higher magnification. This is accomplished by using the main mirror of the telescope itself. To do this you rotate the lever on the right to its vertical position as pictured in the central image above. Leave the lever on the left as is. This rotates a prism into position between the eyepiece and the main body of the scope.

Max Power Mode

There is one further level of magnification avaiable to you. You may have noticed that the eyepiece reads 80x-160x. To achieve the 160x level of magnification rotate the left lever to the upright position. Now both levers should be upright as seen in these images.